1. Field of the Invention
The present invention relates to a heat-assisted magnetic write head used in a heat-assisted magnetic recording in which near-field light is irradiated to lower a coercivity of a magnetic recording medium so as to record information, and a head gimbals assembly, a head arm assembly, and a magnetic disk device mounted with the heat-assisted magnetic write head.
2. Description of Related Art
A magnetic disk device in the related art is used for writing and reading magnetic information (hereinafter, simply referred to as information). The magnetic disk device is provided with, in the housing thereof, a magnetic disk in which information is stored, and a magnetic read write head which records information into the magnetic disk and reproduces information stored in the magnetic disk. The magnetic disk is supported by a rotary shaft of a spindle motor, which is fixed to the housing, and rotates around the rotary shaft. On the other hand, the magnetic read write head is formed on a side surface of a magnetic head slider provided on one end of a suspension, and the magnetic read write head includes a magnetic recording element and a magnetic reproducing element which have an air bearing surface (ABS) facing the magnetic disk. In particular, as the magnetic reproducing element, a magneto-resistive (MR) element exhibiting magneto resistive effect is generally used. The other end of the suspension is attached to an edge of an arm which is rotatably supported by a fixed shaft installed upright in the housing.
When the magnetic disk device is not operated, namely, when the magnetic disk does not rotate, the magnetic read write head is not located over the magnetic disk and is pulled off to the position away from the magnetic disk (unload state). When the magnetic disk device is driven and the magnetic disk starts to rotate, the magnetic read write head is changed to a state where the magnetic read write head is located at a predetermined position over the magnetic disk together with the suspension (load state). When the rotation number of the magnetic disk reaches a predetermined number, the magnetic head slider is stabilized in a state of slightly floating over the surface of the magnetic disk due to the balance of positive pressure and negative pressure. Thus, the information is accurately recorded and reproduced.
In recent years, with a progress in higher recording density (higher capacity) of the magnetic disk, an improvement in performance of the magnetic read write head and the magnetic disk has been demanded. The magnetic disk is a discontinuous medium including collected magnetic microparticles, and each magnetic microparticle has a single-domain structure. In the magnetic disk, one recording bit is configured by a plurality of magnetic microparticles. Since the asperity of a boundary between adjacent recording bits is necessary to be small in order to increase the recording density, the magnetic microparticles need to be made small. However, if the magnetic microparticles are small in size, thermal stability of the magnetization of the magnetic micorparticles is lowered with decreasing the volume of the magnetic maicroparticles. To solve the difficulty, it is effective to increase anisotropic energy of the magnetic microparticles. However, increasing the anisotropic energy of the magnetic microparticles leads to increase in the coercivity of the magnetic disk. As a result, difficulty occurs in the information recording using the existing magnetic head.
As a method to solve the above-described difficulty, a so-called heat-assisted magnetic recording has been proposed. In the method, a magnetic recording medium with large coercivity is used. When recording information, heat is applied together with the magnetic field to a portion where the information is recorded out of the magnetic recording medium to increase the temperature and to lower the coercivity, thereby recording the information. Hereinafter, the magnetic head used for the heat-assisted magnetic recording is referred to as a heat-assisted magnetic write head.
In the heat-assisted magnetic recording, near-field light is generally used for applying heat to the magnetic recording medium. As a method of generating near-field light, a method using a near-field light probe that is a metal strip generating near-field light from a plasmon which is excited by light, that is, so-called plasmon generator is generally known. However, it is known that the plasmon generator which generates near-field light by direct irradiation of light converts the irradiated light into near-field light with extremely low efficiency. A large part of energy of light irradiated to the plasmon generator is reflected by the surface of the plasmon generator or converted into heat energy to be absorbed to the plasmon generator. The size of the plasmon generator is set smaller than the wavelength of light so that the volume of the plasmon generator is small. Therefore, in the plasmon generator, increase of temperature involved with the absorption of heat energy becomes extremely large.
In the heat-assisted magnetic recording, from the viewpoint of the efficiency and the precision, on the surface facing the medium, the generation position of the recording magnetic field and the generation position of the near-field light are desirably approached as much as possible. For example, U.S. Patent Application Publication No. 2007/139818 specification discloses a magnetic head in which a near-field light generation section that generates near-field light in response to irradiation of laser light and an end portion of a main magnetic-pole layer are arranged to be laid over with a dielectric layer in between or directly with each other on a surface facing the medium. In addition, U.S. Patent Application Publication No. 2009/168220 specification discloses a magnetic head in which at least a part of a magnetic pole is arranged between first and second near-field light generation sections that respectively generate near-field light in response to irradiation of laser light. However, if a magnetic pole generating recording magnetic field is arranged near a plasmon generator generating near-field light, the main magnetic pole is heated with increasing the temperature of the plasmon generator. As a result, depending on the humidity condition of the atmosphere, there is a possibility that the main magnetic pole is corroded by moisture in the air.
Consequently, it is desirable to suppress corrosion due to the increase of the temperature of the main magnetic pole from occurring, and to secure long-term reliability while maintaining the recording property.